1. Field of the Invention
Embodiments of the invention relate to devices having feedthroughs for optical waveguides, and more particularly, to hermetically sealed wellhead outlets with feedthroughs that are suitable for use in high pressure, high temperature, and/or other harsh environments.
2. Background Art
In many industries and applications, there exists a need to have small diameter wires or optical waveguides penetrate a partition such as a wall, bulkhead, or wellhead outlet, wherein a high fluid or gas differential pressure can exist across a feedtrough device in the partition. Furthermore, one or both sides of the feedthrough device may be subjected to high temperatures and other harsh environmental conditions, such as corrosive or volatile gas, fluids and other materials. For example, optical sensors, particularly sensors for use in bulkheads or wellhead outlets, oil and gas exploration and production, can require use of a feedthrough device that can seal an optical waveguide at pressures of 20,000 psi and above, and temperatures of 150° C. to 250° C. The wellhead outlets can include a feedthrough where an optical waveguide is concentrically located within a cavity in a housing, and the resulting annular space is filled with a suitable sealant. U.S. Pat. No. 6,526,212, issued Feb. 25, 2003, which is incorporated herein by reference in its entirety, describes in detail an exemplary feedthrough for installation within a bulkhead.
There exist several challenges associated with constructing a feedthrough device and fiber management system for use, for example, in a wellhead outlet. One of these challenges relates to damage and breakage of the fiber at a point where the fiber enters and exits the feedthrough device. The small size of the fiber and the brittle nature of glass materials of the fiber generally make any stress points along the fiber particularly susceptible to damage. For example, damage to the fiber at a stress point where the fiber exits the feedthrough into a low pressure chamber of the wellhead outlet can occur due to a significant stress concentration at that location. Accordingly, movement of the fiber at this stress point as can occur during handling of the wellhead outlet potentially leads to damage of the fiber. Further, the fact that the fiber is rigidly held on one side of the stress point and is free on the other side of the stress point within the low pressure chamber makes the fiber susceptible to damage at the stress point due to micro-bending.
While it is typically desirable to have a length of the fiber extending from the feedthrough for purposes such as splicing, any excess fiber extending from the feedthrough presents storage issues within the wellhead outlet. For example, excess fiber disposed within the low pressure chamber can be disorderly such that the likelihood of damage to the fiber during handling of the wellhead outlet is high, particularly at the stress point discussed above. The disordered arrangement of the fiber within the low pressure chamber permits micro-bends along the length of the fiber extending from the feedthrough and can enable the fiber to become pinched during final assembly of the wellhead outlet such as when a cap is inserted on the low pressure chamber.
Therefore, embodiments of the invention provide optical waveguide feedthrough assemblies and fiber management systems, and methods of making such assemblies, which overcome one or more of the above-described drawbacks and disadvantages of the prior art.